(1) Field of the Invention
The present invention relates to a lock device which locks a lid member hinged to a frame, the lid member being rotatable between an open position and a closed position such that an insertion opening of the frame is opened by the lid member at the open position and closed by the lid member at the closed position.
(2) Description of the Related Art
There is an electronic device frame to which an access door is hinged so as to open or close an insertion opening of the frame. In order to ensure a sealing performance of the frame when the insertion opening is closed, a lock device which is provided to lock the access door in the frame is known.
A conventional lock device of the above type includes a rotatable lever with a lock plate attached thereto, and a fixed member provided at an internal portion of the frame. The rotatable lever is provided on an external surface of the access door, and the lock plate is provided inside the access door. When the lever on the external surface of the access door is rotated to a locked position, the lock plate inside the access door is also rotated so that the lock plate is connected to the fixed member. In this condition, the conventional lock device locks the access door of the frame when the access door is at the closed position. A detailed description will be given of a frame to which a conventional lock device is applied, with reference to FIG. 12 through FIG. 14D.
FIG. 12 shows a frame 100 to which a conventional lock device is applied. The frame 100 is an enclosure case which accommodates an electronic device in which electronic circuits and parts are arranged therein.
As shown in FIG. 12, the frame 100 generally includes a frame main part 112, an insertion opening 113, and an access door 118. The access door 118 is a lid member hinged to the main part 112 by using a pair of hinges 114. The access door 118 is rotatable between an open position and a closed position so that the insertion opening 113 is opened by the access door 118 at the open position and closed by the access door 118 at the closed position. A lock member 110 is attached to the access door 118. The lock member 110 includes a rotatable lever with a lock plate attached thereto, which will be described below.
FIG. 13A and FIG. 13B show a construction of the lock member 110 of the conventional lock device of FIG. 12. FIG. 13A is a perspective view of the lock member 110, and FIG. 13B is a side view of the lock member 110.
As shown in FIG. 13A and FIG. 13B, the lock member 110 includes a rotatable lever 126, a lock plate 127, and a shaft 130. The shaft 130 is provided in the form of a cylindrical slender rod. The lever 126 and the lock plate 127 are secured to both ends of the shaft 130 such that the lever 126 and the lock plate 127 extend in opposite parallel directions from the ends of the shaft 130. When the lever 126 is rotated around the shaft 130, the lock plate 127 is also rotated around the shaft 130 together with the lever 126.
In the conventional lock device of FIG. 12, in order to close the insertion opening 113 of the frame 100, the access door 118 is upwardly rotated on the hinges 114 to the closed position which is shown in FIG. 12. On the other hand, in order to open the insertion opening 113, the access door 118 is downwardly rotated on the hinges 114 to the open position which is not shown in the drawings.
FIG. 14A and FIG. 14B show a condition of the conventional lock device of FIG. 12 when the rotatable lever is set in an unlocked position. FIG. 14A is a front view of the conventional lock device, and FIG. 14B is a cross-sectional side view of the conventional lock device.
As shown in FIG. 14A and FIG. 14B, the access door 118 is set in the closed position, and the lever 126 is set in the unlocked position. In order to lock the access door 118 at the closed position, the lever 126 is downwardly rotated around the shaft 130 to a locked position in a direction indicated by the arrow "X" in FIG. 14A. Hereinafter, a condition of the lever 126 when it is set in the unlocked position will be called a horizontal condition, and a condition of the lever 126 when it is set in the locked position will be called an upright condition.
The conventional lock device includes a fixed member 125 of a thin plate material which is provided at an internal upper portion of the main part 112, as shown in FIG. 14A and FIG. 14B. When the lever 126 is set in the unlocked position, the lock plate 127 at the other end of the shaft 130 is separated from the fixed member 125 of the main part 112.
FIG. 14C and FIG. 14D show a condition of the conventional lock device of FIG. 12 when the rotatable lever is set in the locked position. FIG. 14C is a front view of the conventional lock device, and FIG. 14D is a cross-sectional side view of the conventional lock device.
As shown in FIG. 14C and FIG. 14D, when the lever 126 is set in the locked position, the lock plate 127 at the other end of the shaft 130 is connected to the fixed member 125 of the main part 112. As the lock plate 127 of the lock member 110 is connected to the fixed member 125, the access door 118 at the closed position is locked by the lock member 110, which prevents the access door 118 from being rotated on the hinges 114 to the open position.
However, when the frame 100 is used with the above-described conventional lock device, some problems may arise.
In the conventional lock device of FIG. 12, before the access door 118 is rotated on the hinges 114 to the closed position, the lever 126 must be set in the unlocked position (or the horizontal condition) so as to avoid the interference of the lock plate 127 with the main part 112. After the access door 118 is completely rotated to the closed position at which the access door 118 and the main part 112 are fitted to each other, the lever 126 must be set in the locked position (or the upright condition) so as to ensure a sealing performance of the frame 100. If the lever 126 is set in the upright condition before rotating the access door 118 on the hinges 114 to the closed position, the lock plate 127 at the other end of the shaft 130 may interfere with the main part 112. It is difficult for the conventional lock device in such a condition to completely rotate the access door 118 on the hinges 114 to the closed position without interference. Hence, it is difficult for the conventional lock device in such a condition to ensure the sealing performance of the frame 100.
In the conventional lock device of FIG. 12, when the access door 118 is locked by the lock member 110, the rotation of the access door 118 on the hinges 114 toward the open position is inhibited by the connection of the lock plate 127 and the fixed member 125. In order to maintain the lever 128 in the locked position or the upright condition, it is necessary that an adequate level of a frictional force between the lock plate 127 and the fixed member 125 be exerted. If the adequate level of the frictional force is not exerted, the lock plate 127 is easily disconnected from the fixed member 125 so that the lever 128 is rotated toward the unlocked position or the horizontal condition. This causes the access door 118 to be loosely rotated on the hinges 114 toward the open position. Hence, it is difficult for the conventional lock device in such a condition to ensure the sealing performance of the frame 100.
Further, when the frame 100 is used with the conventional lock device over an extended period of time, the relative position of the lock plate 127 to the fixed member 125 is likely to deviate from the original position due to vibrations or deformations of the frame 100. If the relative position of the lock plate 127 to the fixed member 125 deviates such that the lock plate 127 interferes with the fixed member 125 when the lever 126 is located at an intermediate position between the unlocked position and the locked position, it is difficult to rotate the lever 126 to the locked position. Hence, it is difficult for the conventional lock device in such a condition to ensure the sealing performance of the frame 100.